The commonest type of brake shoe and lining assembly for drum brakes is a brake shoe having a convex, cylindrically curved platform, on the outside of which is attached a replaceable brake lining, usually held in place by rivets.
The use of rivets to attach the brake lining has drawbacks. The riveting procedure usually means that the brake shoe with the lining has to be removed from the vehicle for replacement of the lining. Also, when the lining becomes worn, there is the danger of metal-to-metal contact between the rivets and the brake drum, which is damaging to the drum and seriously reduces braking efficiency.
The prior art includes various designs and proposals for using replaceable brake lining parts in the form of so-called brake plates or brake lining blocks, which include a brake lining fixed to a metal backing plate; such a combination may be attached to the brake shoe more easily than the linings themselves, for example with reusable screws or bolts. Early examples of this type of prior art are shown in the following patents:
U.S. Pat. No. 1,682,319, issued Aug. 28, 1928 to Bluhm, is an early example of such construction, in which cylindrically curved metal plates have brake linings cemented thereto. The linings terminate short of uncovered end portions of the plates, these end portions having holes for receipt of rivets or screws whereby the plates can be connected to an underlying brake shoe platform.
U.S. Pat. No. 2,879,866, issued Mar. 31, 1959 to Newell, shows the use of a brake plate assembly, comprising a metal plate and a brake lining, designed for braking railway wheels, and which can be connected to an exterior brake shoe by rivets.
Several patents indicate that the combination of friction material and metal backing plate may provide an assembly which allows a brake lining to be changed without removing the brake shoe from the vehicle, or, in some cases, without removing either the brake drum or the brake shoe. This can considerably reduce the time needed for replacement of brake linings. Such constructions are shown in the following U.S. patents:
U.S. Pat. No. 3,467,229, issued Sep. 16, 1969 to Deibel;
U.S. Pat. No. 3,941,222, issued Mar. 2, 1976 to Newstead, and
U.S. Pat. No. 4,771,870, issued Sep. 20, 1988 to Belk.
In Deibel, the metal backing plate of the brake plate, to which the brake lining is attached, has inwardly projecting stud members which can slide into axial slots in the brake shoe platform, the brake plate being secured by nuts applied to the stud members inside the brake shoe platform.
In Newstead, the backing plate of each brake plate has integrally formed downwards projections some of which are right angled, and some of which have tongues inside of and parallel to the backing plate. The projections are inserted into apertures in the brake shoe platform, with the tongues engaging the underside of the platform. The brake plate is held in position by fasteners which connect the right-angled projections to the brake shoe.
In Belk, the backing plate has internal nuts welded thereto, which receive bolts connected to flange members of the brake shoe.
Other prior patents include:
U.S. Pat. No. 4,569,424, issued Feb. 11, 1986 to Taylor, which shows threaded bosses in the backing plate which receive fasteners inserted through the brake shoe platform:
U.S. Pat. No. 5,255,762, issued Oct. 26, 1993 to Beri, which shows a construction somewhat similar to that of Belk, in which the threaded bosses are provided by nuts secured to the backing plate, and
U.S. Pat. No. 6,983,831, issued Jan. 20, 2006 to Beri, and corresponding Canadian Patent Application No. 2,542,346, show brake plates in which the corners of the backing plate are held clear of lining material and have bores for rivets whereby they are connected to the brake shoe platform; the backing plate and platform also have further locating and attachment means.
The present invention seeks to overcome, or at least ameliorate, one or more of the disadvantages of these known brake shoe and lining assemblies, and methods of assembling same, or at least provide an alternative.